Field of the Invention
The present invention relates to anti-fatigue compositions, foods which contain such a composition, and uses of such a composition.
Discussion of the Background
Histidine is one kind of basic amino acid, and is an essential amino acid having an imidazoyl group as a heteroaromatic ring in the side chain. Histidine is an amino acid admitted as a food additive, and contained in many foods. For example, histidine is added as a seasoning or flavor-adjusting agent aiming at firm taste, prevention of diffusion of flavor, and the like, and the content thereof is about 50 mg/100 ml at maximum. In relation to the known function of histidine, an anti-fatigue composition containing histidine or histidine hydrochloride is known (see JP-A-2006-137706, which is incorporated herein by reference in its entirety).
Vitamin B6 is one kind of water-soluble vitamin and is a pyridine derivative. Vitamin B6 includes pyridoxine, pyridoxal and pyridoxamine, and they are mutually convertible. They are phosphorylated in the body into pyridoxal 5′-phosphate (PLP) and pyridoxamine 5′-phosphoate, and function as a coenzyme of an enzyme involved in amino acid metabolism such as transamination reaction, decarboxylation reaction and the like. They are also necessary for a reaction to biosynthesize niacin from tryptophan as amino acid, a reaction to biosynthesize glucose 1-phosphate from glycogen, and a reaction to synthesize dopamine and γ-aminobutyric acid as neurotransmitters.
In 2010, vitamin B6 was determined to have the following functions in the “functional claims for food and supplement” issued by EFSA (European Food Safety Authority) (see EFSA Journal 2010; 8(10):1759, which is incorporated herein by reference in its entirety). Normal homocysteine metabolism, maintenance of normal bones/tooth/hair/skin/nail, normal energy-yielding and metabolism, normal psychological function, reduction of tiredness and fatigue, normal cysteine synthesis.
Carnosine is a dipeptide wherein histidine and β alanine are bonded, and is contained in animal-derived foods in large amounts. Carnosine is mainly present in muscles and brain, and a buffering action, an antioxidation action and the like are known (see Amino san no kagaku to saishin ouyou gijiyutsu p. 272-282 CMC Publishing Co., Ltd. 2008, which is incorporated herein by reference in its entirety). It has also been reported that imidazole dipeptide which is a mixture of carnosine and anserine (dipeptide wherein 1 methylhistidine and β alanine are bonded) shows an anti-fatigue effect (see Journal of Clinical and Experimental Medicine, vol. 228, No. 6, p. 722-726, 2009, which is incorporated herein by reference in its entirety).
However, there remains a need for improved anti-fatigue compositions.